Low-Dose Cytarabine in Treating Infants With Down Syndrome and Transient Myeloproliferative Disorder

DISEASE CHARACTERISTICS: * Diagnosis of transient myeloproliferative disorder (TMD) * Diagnosis of Down syndrome or Down syndrome mosaicism (confirmed by karyotype analysis within the past 3 weeks) AND 1 of the following: * Nonerythroid and nonlymphoid blasts (any amount) in the peripheral blood with verification of a second sample * Trisomy 21-positive leukemic blasts documented by biopsy of any organ (including \> 5% nonerythroid/nonlymphoid blasts documented by bone marrow aspirate or biopsy) * Immunophenotype characterization required * High-, intermediate-, or low-risk TMD, as defined by the following: * High-risk TMD, meeting 1 of the following criteria: * Life-threatening cardio-respiratory compromise due to complications of TMD (e.g., organomegaly or effusions) * Life-threatening cardio-respiratory compromise is defined as cardiovascular grade 4 edema, grade 4 pericardial effusions, or grade 4 pleural effusions * Hyperleukocytosis, defined as a WBC \> 100,000/mm³ * Any degree of hepatomegaly (palpable on physical exam) combined with life-threatening hepatic dysfunction * Life-threatening hepatic dysfunction is defined as grade 4 disseminated intravascular coagulation, grade 4 ascites, grade 4 bilirubin (\> 10.0 times upper limit of normal \[ULN\]), or grade 4 AST or ALT (\> 20.0 times ULN) * Intermediate-risk TMD, meeting all of the following criteria: * Hepatomegaly (palpable on physical exam) combined with non life-threatening hepatic dysfunction (i.e., grade 1-3 hepatic dysfunction \[AST or ALT ≤ 2.5 times ULN\] and/or a total or direct bilirubin ≤ 1.5 times ULN) * No evidence of life-threatening cardiovascular, respiratory, or hepatic compromise due to complications of TMD * Low-risk TMD, meeting all of the following criteria: * No palpable hepatomegaly on physical exam OR hepatomegaly is present without hepatic dysfunction (i.e., grade 0 hepatic dysfunction) * No evidence of life-threatening cardiovascular, respiratory, or hepatic compromise due to complications of TMD PATIENT CHARACTERISTICS: * See Disease Characteristics * No biliary atresia by hepatic ultrasound for patients with bilirubin 3.0-10.0 times ULN PRIOR CONCURRENT THERAPY: * No prior antileukemic therapy (except for leukapheresis or exchange transfusion)